How unreliable has Tim Lincecum become for the Giants this season? So unreliable that he has been surpassed by Ryan Vogelsong and possibly Barry Zito in the team’s playoff rotation.

The Giants announced on Sunday that Ryan Vogelsong will start Game 3 of the NLDS. Andrew Baggarly of CSN Bay Area says Barry Zito is expected to pitch if there’s a Game 4, and if not him, Game 1 starter Matt Cain could return to pitch on short rest. That means Tim Lincecum is officially the Giants’ No. 5 starter this year.

This development isn’t really that surprising.

Tim Lincecum’s 5.18 ERA this season is nearly double Matt Cain’s 2.79 mark. He has given up almost two runs more per game than Madison Bumgarner and Vogelsong, and his ERA is a full run higher than Zito’s 4.15.

Managers generally have confidence in pitchers who have proven they can pitch in the postseason, even if they’re having a down season. Lincecum has won two Cy Young Awards and went 4-1 during the Giants’ 2010 World Series championship run. It shows you how badly he’s pitched this season that he’s been bumped this far.

Think about this: Barry Zito, who was a bust of a signing, is now ahead of the two-time Cy Young winner. I suppose that says a lot about both pitchers.